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<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        // const m = new Map();
        // const o = {p: 'Hello World'};

        // m.set(o, 'content');
        // console.log(m.get(o));
        // console.log(m.has(o));
        // m.delete(o);
        // console.log(m.has(o));
        // const m = new Map();
        // const hello = function() {console.log('hello');};
        // m.set(hello, 'Hello ES6')  // 键是函数
        // console.log(m.get(hello));

        const map = new Map([
            [1, 'one'],
            [2, 'two'],
            [3, 'three'],
        ]);
        console.log([...map.keys()]);
    </script>
</body>
</html>